ofio performance for structures and mep seismic

O FiSeismic Vulnerability And Building

Our FirmPerformance For Structures And MEP Equipment

by Kurt R. Lindorfer, S.E.for IEEE San Francisco IEEE / IAS San Francisco

Friday, March 26, Marriott Pleasanton

Copyright Materials: This presentation is protected by US and International Copyright laws. Reproduction, distribution, display and use of the presentation without written permission of

the speaker is prohibitedthe speaker is prohibited.

© PARADIGM Structural Engineers, Inc. 2008

O FiLearning Objectives

Our Firm

+ Gain a more thorough understanding of how buildings perform during earthquakes

+ Evaluate new technologies in structural enhancement & retrofitting

+ Examine methods of protecting MEP equipment and surrounding p g q p ginfrastructure

O FiEvaluating Seismic Risk

Our Firm

O FiEvaluating Seismic Risk

Our Firm

O FiEvaluating Seismic Risk – National

Our Firm

U.S. Geological Survey (USGS) ti l i i h dnational seismic-hazard map

O FiEvaluating Seismic Risk

Our Firm Southeastern US

O FiEvaluating Seismic Risk

Our Firm New Madrid ZoneChicago

St LouisSt. Louis

Little Rock Mississippi Alabama

O FiEvaluating Seismic Risk

Our FirmNew Madrid Zone

+ New Madrid quakes often cited as strongest series of quakes ever known

+ 1811 quake “felt area” is assumed to be 2 million square miles (half the US)

+ Combination of hard bedrock below and loose materials at surface makes potential for damage relatively high and widespread

+ Cities: Memphis St Louis Cape GirardeauCities: Memphis, St. Louis, Cape Girardeau

O FiEvaluating Seismic Risk

Our Firm Western US

O FiHow Buildings Perform During an

Our FirmEarthquake

O FiHow Buildings Perform During an

Our FirmEarthquake

Note: Buildings do not Initially move – the ground moves and the gbuildings respond to the ground motion.

O FiHow a Building’s Shell Performs During

Our Firman Earthquake

Ill t ti f hIllustration of how ground movement imparts acceleration and building di l tdisplacement

O FiHow Buildings Perform During

Our Firman Earthquake

Elastic Inelastic

O FiHow Buildings Perform During an

Our FirmEarthquake (Inelastic Range)

Seattle, WA suffered over 1B damage after the 2001 M6.8 quake

O FiBrief Look at Code Changes

Our FirmRating systems in North America are maturing and experiencing a paradigm shift in the way theyexperiencing a paradigm shift in the way they approach sustainable design:_________________________________+ AWAY from prescriptive methodologies

+ TOWARDS one that emphasizes quantifiable p qperformance_________________________________

NEW Performance- based codes provide clearer guidance than the OLD prescriptive codes taking into consideration the actual growing complexity of the g g p yarchitectural designs

O FiThe “Old” P i ti C dOur FirmPrescriptive Code

+ Acknowledged a design-base earthquake would occurwould occur

+ Lower R – value = less able to dissipate energy

+ Everyone had to trust how the R factor was assigned and design for elastic displacement while acknowledging that a real earthquake would probably be 3 times the severity as the code prescribed = inelastic behavior anticipated and counted upon to dissipate “energy”

O FiCode Changes

Our Firm+ 1989 L P i t & + E i b ildi

Catalysts For Change

+ 1989 Loma Prieta & 1994 Northridge earthquakes

+ Emerging building modeling and technologies

+ New materials+ exhibited damage to buildings and contents that although achieving

+ New materials

+ Inflexible standards inhibited innovativethat, although achieving

“life safety,” exhibited unacceptable levels of non-structural and

inhibited innovative solutions

+ Engineers sought a content damage resulting in lost production and down time.

g gbetter way to depict true building behavior

Retrofitting Technologies

There are effectively 6 Lateral Force Resisting Systems generally used in building construction:

1. Concrete Shearwalls

2. Special Concentric Braced Frames

3. Moment Frames

4. Buckling Restrained Braced Frames

5 Fluid Viscous Dampers5. Fluid Viscous Dampers

6. Base Isolation

Retrofitting Technology: BRFB’s

Retrofitting Technology: BRFB’s

UC Berkeley Stanley Hall Replacement Project (2003)UC Berkeley Stanley Hall Replacement Project (2003)

Retrofitting Technology: Fluid Viscous DDampers

O FiModel Without Fluid Viscous Dampers

Our Firm

O FiModel With Fluid Viscous Dampers

Our Firm

Retrofitting Technology: Base Isolation

Oldest known Base Isolated structure/ buildingMausoleum of Cyrus in Pasargadae (a city in ancient Persia – now Iran)Dates back to VI century BC

Retrofitting Technology: Base Isolation

model on right is base isolatedSource: Cal State University at Northridge

Retrofitting Technology: Base Isolation

• Building moves independently from ground motion

• Most advanced + successful system to limit building damage during a seismic eventbuilding damage during a seismic event

• Optimizes the structure’s response to seismic eventsseismic events

• Allows for continuous operationp

Retrofitting Technology: Base Isolator

Retrofitting Technology: Base Isolation

Retrofitting Technology: Base Isolation

Base Isolation also protects non-structural elements + equipment by reducing the entire structure’s acceleration during

th k d t i f t lan earthquake, as opposed to reinforcement alone.

365 Main Data Center (2002) San Francisco, CA

Retrofitting Technology: Base Isolation

isolators

The Tan Tzu Medical center in Taiwan is currently underThe Tan Tzu Medical center in Taiwan is currently under construction and at 1.7 million square feet is the largest isolated structure in the world. Base Isolation was chosen so that the hospital would be operational immediately after an earthquake.

Retrofitting Technology: Base Isolation(F i ti P d l )(Friction Pendulum)

Retrofitting Technology: Base Isolation(F i ti P d l )(Friction Pendulum)

Retrofitting Technology: Base Isolation(F i ti P d l )(Friction Pendulum)

Mills-Peninsula Health Services Hospital in San Mateo, CA

The ± 450,000 square foot Sutter Health medical facility uses Triple PendulumTM seismic isolation to withstand a magnitude 8 earthquakewithstand a magnitude 8 earthquake.

Mission Critical Operations

PERFORMANCE OBJECTIVE LEVELS

+ LIFE SAFETY• production stoppage Retail/ Commercial

• product loss+ REDUCED DAMAGE

• lost capitalk d bilit t

General Production Facilities• weakened ability to create new product

+ IMMEDIATE OCCUPANCYlost stock

Mission Critical/Essential Services

• lost stock• lose market position

Mission Critical Operations

+ Utilities + Production Facilities

+ Critical Public Infrastructure

+ Life Science Facilities

+ Hospitals+ Data Centers

+ other 24 hr operations+ Laboratories

other 24 hr operations

Mission Critical Operations

Mission Critical Operations

Mission Critical Operations

Mission Critical OperationsCase Study

+ Major Bay Area Pharmaceuticals Company

+ Need to storeproduct in minus 35 degree freezersg

+ In earthquake, faced with not being able to getbeing able to get product out because the building would be red-tagged, or

Structural Solutiongg

product lost entirely

Structural Solution:Solution:

Mission Critical OperationsSolution:+ Encouraged heavy massesheavy masses on upper level floors

+ This building will meet immediate occupancy under DBE and better than life safety under yMCE

+ Paid for enhanced design by “tuning” the foundation capacity to the structure capacity

Mission Critical OperationsCase Study # 2:+ Existing “Pre-Northridge” Moment Frame buildings

+ Balance of Campus had been retrofitted to reduce damage due to “Pre-Northridge” Steel Moment Frame Connections. + Owner desired to reduce risk or known deficiencies and addOwner desired to reduce risk or known deficiencies and add 75,000 SF

Solution

Mission Critical OperationsSolution:+ Attach new 75,000 GSF to both towers, retrofit towers with FVD’sFVD s

+ Total solution increased value of existing assets and paid for it with savings to LFRS of new 75,000 SF story addition.it with savings to LFRS of new 75,000 SF story addition.

Question #1:

Electrical engineers often work with structural engineers on sizing the concrete pad for floor-mounted electrical equipment (i.e. generators, switchgear, etc.,).switchgear, etc.,).

My experience has been that the concrete “housekeeping” pad would be sized about 4” morehousekeeping pad would be sized about 4 more on each side to accommodate anchor bolts, and roughly 4” thick. With the IBC 2006/CBC 2007 requirements, how would this change the rules?

Discussion:

Discussion:

Question #2:

Electrical engineers often have conduit stub-ups going into electrical distribution equipment (i egoing into electrical distribution equipment (i.e. switchgear) for power and/or control wiring. Structural engineers often talk about not h i t d it i t f thhaving too many conduits coming out of the concrete floor because of rebar spacing.

How can this best be corrected? Is there a rule of thumb regarding spacing requirements for conduits we need to be aware of ?we need to be aware of ?

Rules of Thumb:

+ Increase amount of reinforcing to allow for partial bar severing

+ Center to Center spacing of reinforcing (space reinforcing at 8” or 12”) to allow passage of 4” conduitspassage of 4 conduits

+ Create opening in the slab on grade or+ Create opening in the slab on grade or structural slab to allow passage of multiple conduitsconduits

Rules of Thumb:

Question #3:

Electrical engineers are told that flexible connections are required for ceiling mountedconnections are required for ceiling mounted conduits going into electrical distribution equipment from above? Is this true?equipment from above? Is this true?

Discussion:

Question #3 – Part 2:

Does the type of connections needed change if the building is base isolated?change if the building is base isolated?

Discussion:

Question #4:

What would be a good recommendation for specifying concrete rebars etc during anspecifying concrete, rebars, etc., during an earthquake? Spacing issues between the rebar and conduits?

Would spacers work better than concrete-encasing conduits?

Does this also apply for Ufer grounds (concrete encased electrodes)?encased electrodes)?

Discussion:

+ Generally ground does not sever conduits unless crossing over a faultconduits unless crossing over a fault

+ Encasement to protect conduits from future construction activity

+ Also depends on building – copper wire l ld d t t l ill i t= couple welded to steel; will rip out.

Solution = slack in grounding cable

Question #5:

Electrical engineers deal with grounding electrode conductor connections (exothermic or mechanicallyconductor connections (exothermic or mechanically welding) to I-beams. The grounding electrode conductors are usually #4/O AWG or above, but the

th i ldi ti ld b dexothermic welding connection could be severed during an earthquake. It would definitely pose an electrical safety issue if that’s the case.y

Discussion:

OtherOther Q ti ?Questions?